The QuantiDNA? RadTox System is a unique, patented technology that measures tissue damage shortly following injury using cell-free DNA from a drop of blood. Premised on murine and primate studies showing circulating DNA is logarithmically increased with whole-body radiation dose, RadTox has the potential to overcome many of the species-specific challenges faced by biomarker panels. The phase I SBIR for RadTox included assay validation in DiaCarta?s CLIAcertified laboratory and a clinical trial comparing RadTox to the current gold standard for toxicity prediction, the dose-volume histogram. Phase I results confirmed that peak RadTox levels occurred in the first week and that the integral dose, bladder dose, and average peak and day-2 RadTox levels were significantly correlated. The proposed clinical study, powered for personalized toxicity endpoints based on historical observations, is needed to determine if RadTox can outperform dosimetry for toxicity prediction. We expect, for the first time, to subcategorize patients into personalized risk groups. The phase II SBIR will include the following tasks: (1) manufacture RadTox assay kits under GMP; (2) design and implement a clinical utility trial; (3) manage multi-institutional clinical specimen collection, with expert project and contract administration.